Sheet-feeding devices for the cyclic feeding of separated sheets from a sheet feeder to a sheet processing machine or an onward conveying device, such as a tape table, generally include a pair of conveying rollers or draw-off rollers arranged one above another downstream of the sheet stack in the conveying direction. The leading edge of the sheets are fed by transport suckers to the region between the pair of conveying rollers. The conveying rollers or draw-off rollers seize the sheets between them and convey the sheets onwards as a result of their rotation.
Sheet-feeding devices of this type must utilize relatively large diameter conveying rolls and/or draw-off rollers in order to be able to ensure reliable and distortion-free seizing and transporting of the sheets. The large diameter of the conveying or draw-off rollers, however, results in a corresponding long conveying path through the transport suckers, between the sheet stack and the point at which the respectively conveyed sheet can be seized between the conveying rolls or draw-off rollers.
This long conveying path also impacts the elements feeding the sheet to the conveying rolls or draw-off rollers, which in this case comprise what is referred to as a suction head. At the highest possible desired cycle speeds, the movement of the elements of the suction head that feed the sheets is also very rapid, this results in high accelerations and, for reversing the motion for example in the case of the dragging suckers, decelerations of the elements. Because of this rapid movement, however, the loading and the wear of the elements of the suction head and the susceptibility of the elements to defects are also quite high. Additionally, if the sheet feeding device includes a sheet flap between the conveying rolls or draw-off rollers and the sheet feeder, as is generally the case, then the distance between the conveying rolls or draw-off rollers and the sheet stack, and hence the conveying path that has to be overcome by the elements of the sheet feeder that feed the sheet, is even longer. As will be appreciated, this further increases the loading of these elements.